Positivity can be delineated as deterministic positivity or stochastic positivity.[1]}, [2]} Deterministic positivity can be expressed as:
\(\Pr (A=a | \mathbf {Z} = \mathbf {z}) \ge \epsilon > 0 \text{ for } a\in \lbrace 0,1\rbrace  \text{ and } \mathbf {z} \text{ where } p(\mathbf {z}) > 0\) 
